Please Note: This article is written for users of the following Microsoft Excel versions: 2007, 2010, 2013, 2016, 2019, and 2021. If you are using an earlier version (Excel 2003 or earlier), this tip may not work for you. For a version of this tip written specifically for earlier versions of Excel, click here: How Excel Stores Dates and Times.
Written by Allen Wyatt (last updated March 13, 2021)
This tip applies to Excel 2007, 2010, 2013, 2016, 2019, and 2021
Internally, Excel stores a date or time as a number. The whole part of the number (the part to the left of the decimal point) represents the number of days starting with an arbitrary starting point (typically January 1, 1900). The decimal portion (the part to the right of the decimal point) represents the time for that date. These internal representations of dates and times are often referred to as serial numbers.
To see how this works, enter the number 23 in a cell. If you have not previously formatted the cell, Excel uses the General format, displaying the number simply as 23. If you later format this cell using a date format—m/d/yy, for instance—Excel changes the display to 1/23/00, or January 23, 1900. (January 1, 1900, is 1; January 2 is 2; January 3 is 3; and so on.)
The portion to the right of the decimal point represents a fractional portion of a day. Thus, a single second would be equal to approximately 0.00001157407, since that is equal to 1 (a day) divided by 86,400 (the number of seconds in a day).
Since Excel stores dates and times as serial numbers, you can do math on them. For instance, if you wanted to determine the number of days between two dates, or the amount of time between two times, simply subtract them from each other. The result is the number of days and fractions of days between the two.
ExcelTips is your source for cost-effective Microsoft Excel training. This tip (11337) applies to Microsoft Excel 2007, 2010, 2013, 2016, 2019, and 2021. You can find a version of this tip for the older menu interface of Excel here: How Excel Stores Dates and Times.
Professional Development Guidance! Four world-class developers offer start-to-finish guidance for building powerful, robust, and secure applications with Excel. The authors show how to consistently make the right design decisions and make the most of Excel's powerful features. Check out Professional Excel Development today!
When you select a range of cells (particularly if it is a large range of cells), you may not be quite sure if you've ...
Discover MoreExcel allows you to freeze rows or columns in your worksheet so that they don't scroll. How you freeze them can be a bit ...
Discover MoreNeed to share workbook information with a wide number of people? It can be puzzling to figure out which version of Excel ...
Discover MoreFREE SERVICE: Get tips like this every week in ExcelTips, a free productivity newsletter. Enter your address and click "Subscribe."
There are currently no comments for this tip. (Be the first to leave your comment—just use the simple form above!)
Got a version of Excel that uses the ribbon interface (Excel 2007 or later)? This site is for you! If you use an earlier version of Excel, visit our ExcelTips site focusing on the menu interface.
FREE SERVICE: Get tips like this every week in ExcelTips, a free productivity newsletter. Enter your address and click "Subscribe."
Copyright © 2026 Sharon Parq Associates, Inc.
Please Note:
This article is written for users of the following Microsoft Excel versions: 2007, 2010, 2013, 2016, 2019, and 2021. If you are using an earlier version (Excel 2003 or earlier), this tip may not work for you. For a version of this tip written specifically for earlier versions of Excel, click here:
Comments